Wood preservation



Patented Aug. 6,1940

UNHTE STATES PATENT 2,209,970 woon PRESERVATION No Drawing. ApplicationApril Serial. No. 74,963

13 Claims.

The present invention relates to the treatment of wood or similarcellulosic materials and it has particular relation to methods of andcompositions for treating wood for purposes of prevent- 5 ing theattacks of various micro-organisms which cause staining or. decaying ofwood or similar materials.

The main objects of the invention are to provide a composition fordestroying organisms of o deterioration in wood, and for inhibiting thegrowth of such organisms; which is relatively inexpensive to prepare;which does not cause staining of the wood; which is relatively free fromobjectionable odors; which has exceptionally high toxic value againstfungous growths and which retains its protective properties over longperiods of time, even when exposed to relatively intense weathering.

The action of various fungi in producing stain or decay in wood andcellulosic materials has long been recognized. Among the most commonoffenders are green mold, the ordinary blue or sapstaining fungus,Ceratostomella pilifera, and the decay organism, Fomes annosus. Theseare exceptionally active in relatively warm climates such as exist inthe southern part of the United States and are active in green wood'still containing much sap. The sap stain organism does not usuallyproduce pronounced decomposition of the wood in which it grows, butinstead merely produces its characteristic discoloration which suggestsdecay and in substantial amounts results in the reduction of the valueof the lumber for market pur poses. Wood substances, after they havebecome sumciently seasoned, are practically immune from sap stain.

It has heretofore been proposed to protect green lumber during theperiod of seasoning, from sap stain organisms by dipping, spraying, orotherwise applying thereto a suitable toxic substance having theproperty of inhibiting the growth of the organism. Such substance shouldpossess a relatively large number'of characteristics, some" a (I) Itshould be of such nature that it can be .phenol. 'Thesematerials offeredsome advanmade up into a water solution for application but it should beof only slight solubility and volatility when incorporated into lumber.

of; It should be non-corrosive to metals or to w (h) It must not operatedeleteriously to paints and varnishes which may be applied to the wood.

(2) It must penetrate into or adhere to the wood with relative ease.

But few materials are known to possess a sufficient number of theseproperties in an adequate degree to permit of commercial application tolumber. Among the materials heretofore proposed are borax and soda ash.These materials are comparatively inexpensive, non-toxic to animals, andnon-odorous. However, upon weathering, they leach rapidly away. Amongother materials which have been proposed are ethyl mercury chloride, andthe sodium salt of tetrachlortage over borax and soda ash; however,under severe conditions they were not entirely satisfactory. Ethylmercury chloride, for example, is of fairly high volatility and itsconcentration decreases materially upon exposure. It is also ineffectiveagainst green mold. The tetrachlorphenol was not effective incontrolling sap stain fungi growing on softwood species such as pine,spruce, etc. v

The present invention is based on the discovery that pentachlorphenolconstitutes an unusually effective fungicidal material when applied towood or other cellulosic materials and possesses to an unusual degreethe characteristics essential to materials for this purpose.

Pen-tachlorphenol as well as tetrachlorphenol and trichlorphenol haveheretofore been tested by the Petri dish method in malt-agar mediaagainst Ceratostomella pilifera and Fomes annosus. In these tests it wasobserved that the tetrachlorphenol exhibited a very high degree oftoxicity. In contradistinction, it was observed that pentachlorphenolwas of comparatively slight toxicity in the ordinary malt-agar medium.For example: it was found that from .002 to 004% of sodiumtetrachlorphenolate was efiective in the destruction of the ordinary sapstain fungi. About .03% I of pentachlorphenol and more than .1% ofsodium salt of pentachlorphenol was required to produce completedestruction of the fungus. This degree-of toxicity in thepentachlorphenol and its sodium salt was so low as to prohibit itsapplication for destruction of sap stain organism or Fame; annosua in.or upon wood or similar cellulosic material. In view of this observedextremely 55 phenol or, preferably, its sodium salt, are applied to woodthey are substantially more eflective as sap stain inhibitors thantetrachlorphenol compounds. The reason for this reversal of the order ofmerit is obscure and at the present time is not understood. In view ofthe poor showing of the compound in culture media the results withpentachlorphenol compounds were highly surprising.

The pentachlorphenol or its sodium salt are applicable to hard woods orsoft woods of various types, including gum, pine, and the like. Treatingsolutions are prepared by dissolving the sodium salt of pentachlorphenolin water in any suitable ratio. Good results have been obtained by theaddition of three or four pounds of the sodium salt of the phenolcompound to 50 gallons of water. Higher concentrations may be employedbut in general are not required. Substantial reduction of theconcentration results in considerable impairment of the results. Thesolution of the sodium salt of pentachlorphenol may be applied to thewood in any convenient manner. As a general rule it is preferable toapply it to the wood promptly after it has been sawed. It is alsodesirable that the logs themselves be sawed into lumber within a shortperiod after they have been felled in order to prevent premature disecoloration by sap stains. The application of the water solution may bemade by spraying, brushing or dipping. However, for most commercialpurposes dipping seems to constitute the most satisfactory method. Thesawed timberis simply submerged in a suitable bath of the aboveindicated concentration of the sodium salt solutionuntil it isadequately wetted. The timber is then withdrawn from the bath, drainedand permitted to dry. Exposure of the sodium salt of pentachlorphenol tothe carbon dioxide of the air. results in the liberation of thepentachlorphenol in or upon the wood fibers. The free phenol is'of verylow solubility in water andforms a much more permanent fungicide thanthe salt. Accordingly, after dipping, it is desirable that the woodbedried and exposed to the air as thoroughly as possible prior to exposureto rain or other weathering agencies. The phenol may be precipitatedmore quickly by dipping the freshly treated wood into an acid bath or byexposure to an atmosphere containing carbon dioxide in highconcentration. Precipitation of insoluble salts of the phenolate may beeffected by treatment of the wood after it has been treated with sodiumpentachlorphenolate, with a solution of a heavy metal salt such assulfates of zinc, copper or cadmium, or with chloride of barium,mercuric chloride, etc.

The relative merit of pentachlorphenol and certain common andwell-recognized sap stain control chemicals was determined byapplication to freshly cut sticks of pine lumber of 2 inch width, 1 inchthickness, and 18 inch length,

These sticks were dipped into solutions of the various protectivematerials in concentrations of 160 grams per 6 gallons of water and werethen stacked in piles along with similar control sticks which had notbeen treated. The sticks were exposed to'spores of the sap stain andgreen mold organisms carried by wind and various insects, for a periodofsixty days. The piles were then taken down and the specimens wereexamined for the presence. of sap stain. The percentage of the lumberwhich was stained was then estirfiaililted. The raults of the test aretabulated as ows:

Percent Percent stained mold Untreated controls 65. 4 1N gms. sodiumtrichlorphenolste per 6 gals.

water l3. 1 0. 2 160 gms. sodium tetrachlorphenolate per 6 gels.

of water. l2. 8 0. 4 gms. mixture of e ual parts of sodium tri andtetrachlorpheno ate r 6 gals of water.. 11. 8 l. l sodium pentorphenolate per 6 of water 3. l 0. 2 64.4 ms. ethyl mercury chloride per6 gals. of

water 5. 5 l1. 2

The materials were tested under actual mill conditions upon sawed pineat Crossett, Arkansas; Clerks, Louisiana; and Natalbany, Louisiana andthe results of the test indicating the percentage stained are suppliedin the following table:

Crossett Clerks Natalba Chemical concentration Ark L8. LB.

Untreated controls i116 78. 7 8 Eth 1 mercury chloride 1 lb./60 7 8 g as10. 5

Natschlorphenolate 4 lb./50 31 1 1.55 8.6 9.6 Ne-pentachlorphenolate 3lb./50

16.9 1 Na-tetrachlorphenolate 4 lb./50 6 3 2. 36 29. 1 26. 8Na-tetrachlorphenolate 3 lb./50

Ethyl mercury chloride was employed in the amount of 1 pound per 50gallons of water, which is the concentration recommended by itsmanufacturer. At materially higher concentrations it is not economicallyfeasible. It is also understood that higher concentrations do notproportionally increase its eilectiveness. Lumber which has been treatedwith pentachlorphenol after drying in the stack is,found to have a richyelthe other phenols of lower chlorine content. The results of tests ofmixtures of equal parts of tri and tetra, tetra and penta, and penta andtrichlorphenols as applied to sawed pine lumber are given in thefollowing table. In these tests 160 gramsof the mixture of phenols wasincorporated into 6 gallons of water and applied to the lumber bydipping.

Percent of sap stain Percent of green mold 8 r dcd P t erccn Chemicalconcentration to 8 gals. of Stain toxic solution Sodiumtetrachlorphenolate 4 1bs./50 gal.

water.. 27- DO 112 11. Sodium pentachlorphenoiate 4 lira/50 gal. water11. 0 37. 5 9. Do 75 6. Do 300 2.

Other aryl phenols containing alkyl and sulpho groups may also besubstituted for the -butylated and sulphonated phenylphenol; examples ofsuch material are mono and di propylated or butylated derivatives ofsulphonated naphthols or phenol.

Pentachlorphen'ol forms various metallic salts with zinc, magnesium,copper, cadmium, mercury, barium, and the like which may also beemployed for the destruction or prevention of the growth of decayorganisms. These heavy metal salts are preferably made into solutionswith organic solvents such as a lubricating oil, light oils, naphtha,dimethyl ether, wood alcohol and the like. The solutions may be appliedto the dry or seasoned wood by spraying. dipping, or brushing.- However,most effective results are obtained by application of the solution underpressure, thereby causing relatively deep penetration of the compoundsin the wood. Methods such as the full cell method of impregnating woodare well understood and need not be described. In the case of oilsolutions the oil prevents leaching out of the toxic material from thewood and relatively permanent protection is thus obtained. In the caseof dimethyl ether the solvent upon evaporation leaves relativelyinsoluble pentachlorphenol or its insoluble salts deposited in thefibers of the wood itself. Pentachlorphenol and its sodium salt may alsobe dissolved in organic solvents such as dimethyl ether and used toimpregnate lumber against organisms of decay.

Dry or seasoned wood which has been impregn'ated with pentachlorphenoldissolved in a volatile organic solvent or by the sodium salt ofpentachlorphenol dissolved in water or an organic solvent may be furtherimpregnated with soluble salts of copper, zinc, cadmium, mercury, bariumor the like, to precipitate a heavy metal pentachlorphenolate in situ.These pentachlorphenolates are, in most instances, insoluble in waterand provide relatively permanent protective agents for the wood.

Barium pentachlorphenolates is insoluble in cold water but is relativelysoluble in hot water.

Accordingly, wood may be impregnated with a' treated with oil byconventional methods.

. dissolved in any volatilesolvent maybefurther Green or wet woodcontaining substantial amounts of moisture may be submerged in a hotsolution of pentachlorphenol or anyof the salts thereof until the woodis thoroughly heated. The moisture is thus partly ,or completelyvaporized, and upon cooling of the wood while it is submerged, the vaporis condensed and the solution of pentachlorphenol or the salt thereof isdrawn deep into the fibers of the partially evacuated wood to providepermanent protection.

Although onlythe preferred forms of the invention have been described,it will be apparent to those skilled in the art that numerousmodifications may be made therein without departure from the spirit ofthe invention or the scope ofthe appended claims.

What I claim is:

1. A method of treating green wood to prevent the growth of the decayorganism, Fomes annosus, green mold and the sap-staining fungus,Ceratostomella pilifera, without increasing substantially the resistanceof the wood to fire and water or operating deleteriously to paints andvarnishes which may be applied to the wood, which comprises applying tothe wood a solution of a preserving agent selected from the class con-'sisting of pentachlorphenol and the metallic salts thereof, saidsolution being so dilute as not to impart any substantial fire or waterresisting qualities to said wood or to affect deleteriously any paintsor varnishes which may thereafter be applied to the wood and being ofsuflicient concentration to provide substantially adequate protectionagainst the growth of said organisms.

2. A method of treating green wood to prevent the growth therein of thedecay organism, Fomes annosus, green mold and the sap-staining fungus,Ceretostomella pilife'ra, without increasing substantially theresistance of the wood to .fire and water or operating deleteriously topaints and varnishes which may be applied to the wood, which comprisessubmerging the wood at atmospheric pressure in a solution of apreserving agent selected from the class consisting of pentasolutionbeing so dilute as not to impart any substantial fire or water resistingqualities to saidwood or to affect deleteriously any paints or varnisheswhich may be thereafter applied to the wood and being of suflicientconcentration to provide substantially adequate protection against thegrowth of said organisms, and subsequently subjecting the resulting woodto drying and seasoning in air.

3. A method of treating green wood to prevent the growth therein of thedecay organism, Fomes annosus, green mold and the sap-staining fungus,C'eratostomella pilifera, without increasing substantially theresistance of the wood to fire and water or aiiecting deleteriouslypaints and varnishes which may be applied to the wood, which comprisesapplying to the wood a solution of pentachlorphenol, said solution beingso dilute as not to impart any substantial fire or water resistingqualities to said wood or to affect deleteriously any paints orvarnishes which may be thereafter applied to the wood and being ofsufficient concentration to provide substantially adequate protectionagainst the growth of said organisms.

4. A method of treating green wood to prevent the growth therein of thedecay organisms, Fomes annosus, green mold and the sap-staining fungus,

Ceratostomella pat/era, without increasinl substantially the resistanceoi the wood to fire and water or aflecting deleteriously paints andvarnishes which may be applied to the wood, which comprises applying tothe wood an aqueous solution of sodium pentachlorphenolate,-saidsolution being so dilute as not to impart any substantial fire or waterresisting qualities to said. wood or to afl'ect deleteriously any paintsor varnishes which may be thereafter applied to the wood and being ofsuflicient concentration to provide sulistantially adequate protectionagainst the growth of said organisms.

5. A method of treating green wood to prevent growth of sap stainorganisms therein, comprising applying thereto an aqueous solution oi amixture of the metallic salts of tri and pentachlorphenols.

6. A wood preservative which comprises a mixture of a pentochlorphenolsalt and an alkylated and sulphonated aryl phenol.

7. A wood preservative which comprises a mixture of a pentachlorphenolsalt and a di-propyl sulphonated naphthol.

8. A wood preservative which comprises a mixture of a pentachlorphenolsalt and a di-butyl sulphonated naphthol.

9. A wood preservative which comprises a mixture of a pentachlorphenolsalt and a sodium salt of sulphonated and butylated phenyl phenol.

10. A wood preservative which comprises a mixture 01' a pentachlorphenolsalt and an allgvlated and suiphonated phenol.

11. A method of protecting wood from iungous growths which comprisesapplying to the wood a solution of a salt of pentachlorphenol, in whichsolution water is employed as a solvent and an alkylated and sulphonatedphenol is employed as an adiuvant.

12. A method of treating green wood to prevent the growth of sap stainorganisms thereupon which comprises treating the lumber with a watersolution 0! sodium pentachlorphenolate and an alkylated and sulfonatedphenol.

13. A method as defined in claim 12 in which the alkylated andsuiphonated phenol is a sulphonated and butylated phenylphenol.

HAROLD R. HAY.

